Skechers Slip-in Ultra Flex 3.0 Crochet Knit Sandals - Pretty Combo. Enjoy sunny days in breezy comfort with Skechers Hands Free Slip-ins : Ultra Flex 3.0 - Pretty Combo. Designed with our Heel Pillow-, this slingback sandal features a knitted strap upper with a back heel and a cushioned Yoga Foam footbed._Textile and manmade upper. Content: textile and manmade upper. Sole thickness: 1 6/8". Fit: true to size. COO: Imported.